Tsukahara Noriyuki, Minamitani Emi, Kim Yousoo, Kawai Maki, Takagi Noriaki
Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan.
RIKEN, 2-1 Hirosawa, Saitama 351-0198, Japan.
J Chem Phys. 2014 Aug 7;141(5):054702. doi: 10.1063/1.4890654.
Iron(II) phthalocyanine (FePc) molecule causes novel Kondo effects derived from the unique electronic structure of multi-spins and multi-orbitals when attached to Au(111). Two unpaired electrons in the d(z)(2) and the degenerate dπ orbitals are screened stepwise, resulting in spin and spin+orbital Kondo effects, respectively. We investigated the impact on the Kondo effects of the coordination of CO and NO molecules to the Fe(2+) ion as chemical stimuli by using scanning tunneling microscopy (STM) and density functional theory calculations. The impacts of the two diatomic molecules are different from each other as a result of the different electronic configurations. The coordination of CO converts the spin state from triplet to singlet, and then the Kondo effects completely disappear. In contrast, an unpaired electron survives in the molecular orbital composed of Fe d(z)(2) and NO 5σ and 2π* orbitals for the coordination of NO, causing a sharp Kondo resonance. The isotropic magnetic response of the peak indicates the origin is the spin Kondo effect. The diatomic molecules attached to the Fe(2+) ion were easily detached by applying a pulsed voltage at the STM junction. These results demonstrate that the single molecule chemistry enables us to switch and control the spin and the many-body quantum states reversibly.
当铁（II）酞菁（FePc）分子附着在Au(111)上时，由于其多自旋和多轨道的独特电子结构，会产生新颖的近藤效应。d(z)(2)和简并dπ轨道中的两个未配对电子会被逐步屏蔽，分别导致自旋近藤效应和自旋+轨道近藤效应。我们使用扫描隧道显微镜（STM）和密度泛函理论计算，研究了CO和NO分子与Fe(2+)离子配位作为化学刺激对近藤效应的影响。由于电子构型不同，这两种双原子分子的影响彼此不同。CO的配位将自旋态从三重态转变为单重态，然后近藤效应完全消失。相反，对于NO的配位，一个未配对电子存在于由Fe d(z)(2)和NO 5σ及2π*轨道组成的分子轨道中，导致尖锐的近藤共振。峰的各向同性磁响应表明其起源是自旋近藤效应。通过在STM结处施加脉冲电压，附着在Fe(2+)离子上的双原子分子很容易被分离。这些结果表明，单分子化学使我们能够可逆地切换和控制自旋以及多体量子态。
